1. Field of the Invention
Generally, the present invention relates to an optical radiation sensor system.
2. Description of the Prior Art
Optical radiation sensors are known and find widespread use in a number of applications. One of the principal applications of optical radiation sensors is in the field of ultraviolet radiation fluid disinfection systems.
It is known that the irradiation of water with ultraviolet light will disinfect the water by inactivation of microorganisms in the water, provided the irradiance and exposure duration are above a minimum xe2x80x9cdosexe2x80x9d level (often measured in units of microWatt seconds per square centimetre). Ultraviolet water disinfection units such as those commercially available from Trojan Technologies Inc. under the tradenames UV700 and UV8000, employ this principle to disinfect water for human consumption. Generally, water to be disinfected passes through a pressurized stainless steel cylinder which is flooded with ultraviolet radiation. Large scale municipal waste water treatment equipment such as that commercially available from Trojan Technologies Inc. under the trade-names UV3000 and UV4000, employ the same principal to disinfect waste water. Generally, the practical applications of these treatment systems relates to submersion of treatment module or system in an open channel wherein the wastewater is exposed to radiation as it flows past the lamps. For further discussion of fluid disinfection systems employing ultraviolet radiation, see any one of the following:
U.S. Pat. No. 4,482,809,
U.S. Pat. No. 4,872,980,
U.S. Pat. No. 5,006,244,
U.S. Pat. No. 5,418,370,
U.S. Pat. No. 5,539,210, and
U.S. Pat. No. 5,590,390.
In many applications, it is desirable to monitor the level of ultraviolet radiation present within the water under treatment. In this way, it is possible to assess, on a continuous or semi-continuous basis, the level of ultraviolet radiation, and thus the overall effectiveness and efficiency of the disinfection process.
It is known in the art to monitor the ultraviolet radiation level by deploying one or more passive sensor devices near the operating lamps in specific locations and orientations which are remote from the operating lamps. These passive sensor devices may be photodiodes, photoresistors or other devices that respond to the impingent of the particular radiation wavelength or range of radiation wavelengths of interest by producing a repeatable signal level (in volts or amperes) on output leads.
Conventional ultraviolet disinfection systems often incorporate arrays of lamps immersed in a fluid to be treated. Such an arrangement poses difficulties for mounting sensors to monitor lamp output. The surrounding structure is usually a pressurized vessel or other construction not well suited for insertion of instrumentation. Simply attaching an ultraviolet radiation sensor to the lamp module can impede flow of fluid and act as attachment point for fouling and/or blockage of the ultraviolet radiation use to treat the water. Further, there is an increasing desire to utilize ultra-violet disinfection systems to treat relatively low quality waterxe2x80x94e.g., low quality waste water from municipal waste water treatment plants. This creates a problem in that those components of the disinfection system which are in continued contact with the waste water will accumulate fouling materials. The accumulation of fouling materials on an ultra-violet radiation sensor can lead to the conveyance of misleading information to the operator about the status of the ultra-violet radiation sources. In other words, as the sensor accumulates fouling materials, its ability to sense ultra-violet radiation will be reduced. A corresponding signal would be sent to the operator who might mistake the signal for an indication that one or more of the radiation sources is not operating. Further, placing a cleaning mechanism for the sensor surface in the flow of fluid is problematic since this can impede the flow of fluid and act as an attachment point as described hereinabove.
Accordingly, it would be desirable to have an optical radiation sensor system having a surface which could be periodically cleaned while the fluid treatment system is in operation. It would be particularly advantageous if the surface of the sensor device could be cleaned in a manner which minimized or avoided impeding of the flow of fluid through the fluid treatment system.
It is an object of the present invention to provide a novel radiation source module which obviates or mitigates at least one of the above-mentioned disadvantages of the prior art.
It is another object of the present invention to provide a novel radiation source assembly which obviates or mitigates at least one of the above-mentioned disadvantages of the prior art.
Accordingly, in one of its aspects, the present invention provides an optical radiation sensor system for detecting radiation from a radiation field, the device comprising:
a sensor device for detecting and responding to radiation from the radiation field, the sensor device comprising a surface, the surface being movable with respect to the radiation field between a first position in which the surface is within the radiation field and a second position in which at least a portion of the surface is without the radiation field; and
a cleaning device for removing fouling materials from at least a portion of the surface in the second position.
Thus, the present inventors have discovered an optical radiation sensor system which allows for in situ cleaning of the surface of the sensor device which receives radiation. Generally, it is preferred that the present optical radiation sensor system achieves such cleaning of the surface while the surface is being moved or has been moved with respect to the field of radiation. Many advantages accrue from this approach. First, cleaning of the surface may be achieved independently of the flow of fluid thereby avoiding leakage of cleaning agent (if used) into the flow of fluid and minimizing or obviating hydraulic head loss penalties which would result if the structural elements used to clean the surface of the sensor device were placed in the flow of fluid. Second, servicing of the sensor device is facilitated. Third, the present approach facilitates the use of mechanical cleaning, chemical cleaning or a combination of chemical/mechanical cleaning of the surface. Other advantages will become apparent to those of skill in the art.